This document conditionally approves a revision to the Ohio State Implementation Plan (SIP) to meet the requirements of the USEPA transportation conformity rule. The transportation conformity SIP revisions enable the State of Ohio to implement and enforce the Federal transportation conformity requirements at the State or local level. The Federal transportation conformity rule has been amended twice since the original 1993 publication, and the Ohio SIP will need to be amended to accommodate the changes. The purpose of transportation conformity is to assure that transportation plans, programs and projects, approved by the United States Department of Transportation conform to the purpose of the SIP to attain and maintain the public health based air quality standards. The rationale for this conditional approval and other information are provided in this document.